But a spokesman for the builder, Calpine Corp., said the company wouldn't move ahead with its Russell City Energy Center without a power contract. A long run of low wholesale electricity prices has made the company cautious about new construction, said company spokesman Kent Robertson.

Calpine had planned to begin construction next spring on the natural gas- fired plant. The plant was expected to be generating electricity for 600,000 customers in the summer of 2005.

"We're not moving into new construction of plants without power purchasing contracts. Russell City is no different," Robertson said. "Current market conditions are an obstacle to construction at this time."

The project, approved unanimously by the five-member commission, is planned for a 15-acre site at Enterprise and Whitesell streets. Its main water supply will be secondary waste water from the nearby Hayward water pollution control plant. An advanced water treatment plant will be built as part of the project and will become the property of the city of Hayward.